/Engine/Source/Runtime/Engine/Public/Materials/MaterialRenderProxy.h
Defines a scope to update deferred uniform expression caches using an async task to fill uniform buffers. The scope attempts to launch async updates immediately, but further async updates can launch within the scope. Only one async task is launched at a time though. The async task is synced when the scope destructs. The scope enqueues render commands so it can be used on the game or render threads.
class FUniformExpressionCacheAsyncUpdateScope